1. Field of the Invention
The present invention relates to a pipe joint structure, in which a protrusion of a pipe is press fitted to a connector of the pipe joint structure, and also relates to a manufacturing method of such a pipe joint structure.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 2002-192203 (corresponding to US2004/0036277A1) discloses a pipe joint structure and a manufacturing method thereof. The disclosed pipe joint structure is used, for example, in a refrigerant pipe line arrangement of a refrigeration cycle of a vehicle air conditioning system and includes a connector and two pipes. Two through holes penetrate through the connector in a thickness direction of the connector. An enlarged recess is provided in the connector at one axial end of each through hole. The enlarged recess has a size greater than an inner diameter of the through hole. Each through hole of the connector receives the corresponding pipe in such a manner an annular protrusion formed near an axial end of the pipe is securely press fitted into the enlarged recess.
In the above pipe joint structure, only the annular protrusion of each pipe is securely press fitted into the corresponding enlarged recess of the connector. In such a case, when the pipe joint structure is constructed to have a small space between each pipe and an inner peripheral surface of the corresponding through hole, the pipe could be loosened upon application of an external force to the pipe in some circumstances. The loosening of the pipe could cause removal of the press fitted annular protrusion of the pipe from the enlarged recess. This loosening of the pipe is probably due to the fact that the pipe is secured to the connector only through the connection achieved by the press fitting between the annular protrusion of the pipe and the enlarged recess of the connector. This single point connection between the pipe and the connector may not provide a sufficient connecting strength for connecting between the pipe and the connector in some circumstances.
In a case where an end opening of the end of each refrigerant pipe, which is located near the connector, is connected to an opening of another member by, for example, brazing, relatively small tolerance limits (e.g., about ±0.1) are required in a pith size of the refrigerant pipe at the end opening thereof. However, in the case where the refrigerant pipe is press fitted to the connector, the tolerance is increased (e.g., about ±3.0) in general. Therefore, in some cases, an additional step of adjusting the size of the refrigerant pipe may be performed by, for example, applying a external force, such as a torsional force or a flexural force, to the refrigerant pipe after the press fitting of the refrigerant pipe to the connector, and such an external force could release the press fitted connection between the refrigerant pipe and the connector.